A semiconductor memory device may include at least one semiconductor such as silicon Si, germanium Ge, gallium arsenide GaAs, indium phosphide InP, etc. A semiconductor memory device may be classified as a volatile semiconductor memory device or a nonvolatile semiconductor memory device.
A volatile memory device loses its stored data when its power supply is interrupted. Examples of the volatile memory device include a static RAM (SRAM), a dynamic RAM (DRAM), a synchronous DRAM (SDRAM), etc. A nonvolatile memory device retains its stored data even when its power supply is interrupted. Examples of the nonvolatile memory device include a read only memory (ROM), a programmable ROM (PROM), an electrically programmable ROM (EPROM), an electrically erasable and programmable ROM (EEPROM), a flash memory, a phase change RAM (PRAM), a magnetic RAM (MRAM), a resistive RAM (RRAM), a ferroelectric RAM (FRAM), etc.
As a semiconductor technology is developed, a storage device based on a flash memory is being developed. A flash memory reads or writes data by a page unit and performs an erase operation by a block unit. Even though a flash memory has a high read speed compared with a conventional hard disk, it has a physical characteristic that cannot perform an overwrite operation. A lot of time may be consumed in an erase operation due to the physical characteristic of the flash memory.